Transient Receptor Potential Canonical (TRPC) Ca2+permeable channels play critical roles in cardiovascular physiology. TRPCs are now also recognized as critical components in signaling processes associated to several cardiovascular diseases. Nevertheless, the potential function of TRPCs in molecular and cellular events associated to atherosclerosis, the major cause of coronary artery disease in western societies, remains largely unexplored. Atherosclerosis is characterized by a maladaptive inflammatory response that takes place in the subintima, where endothelial inflammatory signaling, adhesion molecules, recruitment of circulating monocytes and survival/apoptosis of lesional macrophages are all fundamental components in progression and fate of the atherosclerotic lesion. Improving our understanding of and identifying new signaling components in those processes is of key importance to develop new and alternative therapeutic strategies for the disease. By examining a novel role of the channel forming protein TRPC3 in the mechanisms associated to monocyte recruitment and macrophage survival, this proposal contributes to that goal and also provides an opportunity to fill an important gap of knowledge in the TRPC field. Work from our group shows that TRPC3 is fundamental in the signaling driving VCAM-1 expression/function in coronary endothelium and in the mechanisms underlying macrophage survival. The general hypothesis is therefore proposed that TRPC3 channel, in the inflammatory setting of atherosclerotic lesion formation, is a contributing factor to the mechanisms involved in lesion progression by virtue of its roles in endothelial expression/function of VCAM-1 and in the survival of lesional macrophages. The long term goal of the project is to understand the impact of TRPC3 activity on endothelial inflammatory signaling, monocyte recruitment and macrophage survival/apoptosis. It is our hope that the information derived from these studies may help rationalize future translational/clinical studies and that they will provoke additional efforts to understand the role of TRPC3 in this and other vascular diseases. The experiments proposed in Specific Aim 1 are designed to examine the role of endothelial TRPC3 in atherogenesis by investigating, in vitro, the contribution of TRPC3 to the signaling associated to VCAM-1 expression and function, and in vivo, the characteristics of atherosclerotic lesions in endothelial-specific TRPC3 transgenic and knockout mouse models of atherosclerosis. Studies in Specific Aim 2 will examine the role of TRPC3 in macrophage survival and apoptosis in vitro, and how such role influences atherogenesis by using macrophage-specific TRPC3 deficient mice. In vitro studies are proposed using wild-type and TRPC3-deficient macrophages to examine their responsiveness to different pro-apoptotic stimuli, status of survival signaling pathways and efferocytosis. In vivo, a longitudinal study is proposed to examine the characteristics of early and advanced lesions using lethally-irradiated LDLR-/- mice reconstituted with bone marrow from macrophage-specific TRPC3-/- animals.